TABLE OF CONTENTS (TTS 503-1)     

 

ROLLING RESISTANCE (RR) 

    TIRE ROLLING RESISTANCE   

         Pneumatic tire construction 

         Tire spring rate       

         Tire deformation, static loaded radius         

         Tire footprints         

         Tire crawl    

         Primary mechanisms of tire rolling resistance          

         Tire developed length         

         Static and effective tire radius         

         Tire angular velocities and radians   

         Coefficient of Rolling Resistance "f"  

    EFFECT OF:

      Tire Speed   

      Critical speed and standing waves    

      Force variations       

      Tire aging and service life    

      Inflation pressure & road surface     

      Tire diameter          

      Road surface quality (roughness)     

      Water, slush and snow        

      Tire section  

      Distribution of the energy loss         

      Tire load and speed ratings  

      Magnitude of the tire resistance forces         

    TIRE FRICTION AND TRACTIVE EFFORT LIMITS

       Road adhesion coefficient μ  

       Tire slip       

       Tractive force vs. longitudinal slip

   

    MECHANICAL ROLLING RESISTANCE       

      The power-on and power-off conditions       

      Hypoid gearset friction loses 

      Universal and constant velocity joints          

      Universal (cross type) joints 

      Constant velocity (CV) joints           

      Double cardan joint  

      CV joint assemblies  

      Ball and Trunnion Tripod joints        

      Rzeppa CV joint       

      Friction characteristics of universal and CV joints            Brake drag

 

AIR RESISTANCE (RA)          

    PROPERTIES OF AIR   

       Standard air 

    COMPONENTS OF AIR RESISTANCE    

       Form drag   

       Internal flow drag    

       Surface drag           

       Lift drag      

       Interference drag     

    THE AIR RESISTANCE FORCE 

       Effect of air density on R_A    

       Vehicle frontal area (A)        

       Drag coefficient (Cd)           

       Range of Cd values for objects and ground vehicles          CdA 

       Simplified expression for R_A  

       Air resistance horsepower    

       Lateral wind forces – yaw angle ψ    

       Center of pressure CP         

       Aerodynamic pitching, yawning and rolling moments

GRADE RESISTANCE (RG)    

      Measurements of road grades          

      Range of road grades in the USA     

      Calculation of grade resistance force 

      The downhill runaway grade pull problem    

 

INERTIA (RI)  

      Inertia Defined        

      Vehicle mass           

      Effective vehicle mass for Power-On conditions        

      Single equivalent rotating mass factor γ      

      Calculating the mass factor γ           

      Determination of Inertia Resistance  

 

ACQUIRING VEHICLE  ROAD LOAD VALUES           

      Kinetic Energy (K) defined   

      Using coastdowns to determine vehicle road loads          Effective vehicle mass for power-off conditions        

      Measuring elapsed time       

      Choosing the coastdown speed intervals      

      Speedometer calibration      

      Weighing the vehicle & determination of mass         

      Quick assessment of vehicle changes          

      Choosing the coastdown road surface          

      Determination of average decelerations       

      Coastdown test example      

      Vehicle mass           

      Decelerations thru a speed interval  

      Average road load forces for the speed interval        

      Plotting the road load profile 

      Road loads in terms of the power loss         

 

AUTOMOTIVE POWERTRAINS          

    DRIVE TORQUE VS. TRACTIVE EFFORT REQUIREMENTS

       Ideal torque/power characteristics of auto powerplants

       Actual torque/power characteristics of gasoline engines       Actual torque/power characteristics of Diesel engines

    ROLE OF GEAR CHANGE TRANSMISSION       

       Gear Ratio selection 

       Overall geared reduction     

       Geometric ratio Series         

       Advantages of geometric gear reduction series        

    TRANSMISSIONS AND VEHICLE FUEL EFFICIENCY     

 

THE VEHICLE PERFORMANCE ENVELOPE    

    PERFORMANCE CONSTRAINTS & BOUNDARIES          

       The level, hard surfaced road boundary       

       Characteristic vehicle acceleration curves     

       Maximum vehicle speed       

       Tractive effort boundary      

       Tire traction limitations        

       The “Right Side” boundary   

       Performance objectives and boundaries set by         

       the vehicle engineer 

       Constant maximum horsepower       

       Gradeability and acceleration are coupled requirements